Washability Testing Explained: How Scrub Resistance Testing Works and Why It Matters

Overview of washability testing

Washability testing evaluates how well a paint, coating, varnish, or ink withstands the mechanical stress of cleaning. It is one of the most widely specified durability tests in the coatings industry, informing product development decisions, quality control processes, and regulatory compliance across architectural paints, industrial coatings, and printed packaging. 

Understanding washability is essential for manufacturers and formulators who need to predict real-world coating performance. A coating that fails under repeated scrubbing may degrade prematurely on walls, packaging surfaces, or industrial substrates – leading to product recalls, customer complaints, and reputational risk. 

What Does Washability Testing Asses?

Washability tests assess coating durability under simulated cleaning conditions. The key performance indicators evaluated include: 

• Scrub resistance – the number of cycles a coating withstands before visible wear, film removal, or substrate exposure occurs 
• Color retention – whether the coating maintains its original color after abrasion 
• Gloss retention – how well the surface sheen is preserved after repeated cleaning 
• Film thickness loss – the degree of material removal measured by weight or optical inspection 

These measurements help manufacturers establish performance grades, compare formulations, and demonstrate compliance with applicable standards. 

Equipment and Setup

Washability testing is performed on a motor-driven scrub abrasion tester. The TQC Sheen Scrub Abrasion and Washability Tester (AB6000 / AB6010) is the leading instrument in this category, manufactured by TQC Sheen, Industrial Physics’ specialist paint and coating testing brand. 

The tester drives a scrubbing tool back and forth across a coated test panel at precisely controlled speed and stroke length. Key setup parameters include: 

• Stroke length: adjustable from 20-300 mm 
• Traverse speed: 1-60 cycles per minute 
• Testing medium: water, detergent solution, or dry abrasive media (depending on the standard) 
• Scrubbing tool: brush, sponge, pad, or cloth – selected according to the test standard 
• Sample dimensions: max panel length 350 mm, max width 70 mm, max thickness 35 mm 

 The AB6000 model supports both wet and dry testing via an integrated pump system with a flow rate of 0.0-3.0 ml per minute. The AB6010 is a dry-testing-only variant. Both models use a precision micro-step controlled electro motor and sinus waveform speed control for consistent, repeatable results. 

Wet vs. Dry Washability Testing

The distinction between wet and dry testing is determined by the standard being followed and the intended end-use environment of the coating: 

• Wet testing simulates cleaning with water or detergent – relevant for architectural paints, wall coverings, and food-contact packaging surfaces 
• Dry testing assesses resistance to dry friction and abrasion – relevant for industrial coatings, automotive finishes, and surface films 

Some standards – such as ISO 11998 – specify wet-scrub resistance explicitly, while others such as ASTM D2486 allow for both conditions depending on the formulation being evaluated.

The Test Procedure – Step by Step

The distinction between wet and dry testing is determined by the standard being followed and the intended end-use environment of the coating: 

• Wet testing simulates cleaning with water or detergent – relevant for architectural paints, wall coverings, and food-contact packaging surfaces 
• Dry testing assesses resistance to dry friction and abrasion – relevant for industrial coatings, automotive finishes, and surface films 

Some standards – such as ISO 11998 – specify wet-scrub resistance explicitly, while others such as ASTM D2486 allow for both conditions depending on the formulation being evaluated. 

1. Apply the coating to the test panel using a film applicator and allow it to cure fully according to the manufacturer specifications. 
2. Mount the coated panel on the tester flat bed and secure it in position. 
3. Select the appropriate scrubbing tool and apply the specified load as defined by the relevant standard. 
4. If performing wet testing, introduce the test solution at the specified pump flow rate. 
5. Set the stroke speed and total cycle count as defined by the standard or test protocol. 
6. Run the test to completion – either to a fixed number of cycles (pass/fail) or until failure occurs (progressive testing). 
7. Evaluate results by visual inspection, weight loss measurement, or optical analysis depending on the standard. 

Applicable Test Standards

The TQC Sheen AB6000 and AB6010 are designed to comply with the following internationally recognized standards: 

• ASTM D2486 – Standard test method for scrub resistance of wall paints 
• ASTM D4213 – Scrub resistance of paints by abrasion weight loss 
• ASTM D4828 – Practical washability of organic coatings 
• ASTM D3450 – Washability properties of interior architectural coatings 
• ISO 11998 – Determination of wet-scrub resistance and cleanability of coatings 
• DIN 53778 – Resistance of paint coatings to scrubbing and cleaning 

The modular accessory system allows operators to reconfigure the instrument to comply with multiple standards without purchasing separate equipment, significantly reducing laboratory costs. 

Interpreting Results

Results are reported in one of two ways depending on the test methodology: 

• Pass/fail: the coating survives a defined number of scrub cycles without visible deterioration – common in product conformance testing 
• Cycles to failure: the number of strokes at which the coating first shows measurable wear – used in comparative product development testing 

Additional analysis – such as color difference (delta E) measurement or gloss retention percentage – can be conducted post-test to characterize the degree of degradation in greater detail. 

Common Errors and Best Practices

• Ensure complete curing of the coating before testing. Under-cured films produce misleadingly poor results. 
• Select the correct scrubbing tool and load for the standard. Using the wrong accessory invalidates the test. 
• Keep test conditions consistent between runs – temperature and humidity can affect both the coating and the scrubbing medium. 
• Use the Camera Tool Kit accessory to automate visual pass/fail detection and reduce operator subjectivity. 
• Always calibrate the instrument with the correct weights before testing.